This invention relates to a driving controller and an image sensing apparatus which is provided with such a driving controller, in particular to a driving controller which is useful for a driving mechanism including a plurality of driving units having a driven member and a driving member are held by a frictional engagement.
A driving unit has been conventionally known which includes an impact-type piezoelectric actuator constructed such that a driven member having a taking lens or the like mounted thereon is so coupled to a bar-shaped driving member to have a specified frictional force and a piezoelectric element is secured to one end of the driving member. An electronic apparatus, e.g., image sensing apparatuses, using such a driving unit are also known (for example, see Japanese Unexamined Patent Publication No. 2001-103772).
In the driving unit including the impact-type piezoelectric actuator, if the driven member and the driving member are left in contact for a long time without being driven, the driving member and the driven member are adhered to each other by resin on the outer surface of the driving member. Thus, there has been an undesirable possibility that the driven member is not driven even if a drive voltage is applied to the driving unit.
In order to solve such a problem, a way of releasing a driven member and a driving member from an adhered state by changing a driving frequency and a drive voltage has been proposed (for example, see Japanese Unexamined Patent Publication No. 2001-184757).
However, a vibration motor or ultrasonic motor in the latter publication is such that a ring-shaped piezoelectric element formed on one end surface of a resilient vibrator or stator is excited to generate a progressive wave on the outer surface of the stator, and a slider is pressingly mounted on the stator at a specific pressure to be driven by a frictional force acting between the slider and the stator. Thus, for such an actuator as to drive a driven member engaged with the driving member with a specific frictional force by securing one end of the layered piezoelectric element to a supporting member and the other end thereof to a rod-shaped driving member and causing the piezoelectric element to elongate and shrink, the driven member and the driving member cannot be released from the adhered state in some cases according to the way of the latter publication.